Estimation of the weight-length relationship and condition factor of three main fish species in the coastal region of the southern zone of São Tomé and Principe Island

Wilfred Boa Morte Zacarias; Richard Kindong; Tommy Melo; Merian Gorett Monte Verde Gomes Cravid; Xiaojie Dai

Estimation of the weight-length relationship and condition factor of three main fish species in the coastal region of the southern zone of São Tomé and Principe Island

Authors
Wilfred Boa Morte Zacarias, Richard Kindong, Tommy Melo, Merian Gorett Monte Verde Gomes Cravid, Xiaojie Dai

Abstract
This study was developed with the objective to estimate the Length-Weight Relationship (LWR) and condition factor of three main fish species collected by artisanal fishermen in the coastal region and in the mangroves of the South zone of São Tomé Island. This study focused on species of greater economic value and importance; these species are: Dentex macrophthalmus, Lethrinus atlanticus, and Lutjanus fulgens. The sampling duration was between March and October, 2019, using hand line, bottom longline, and vertical longline gears. Potential regression analysis was performed to study the length-weight relationship W=a.FLb

; and the respective exponential equations for the LWR relationship are Dentex macrophthalmus (Wt = 0,0152 (FL)^2,9801 Lethrinus atlanticus (Wt = 0,0159 (FL)^2,9778, Lutjanus fulgens (Wt 0,0115 (FL)^3,0581. In the present study, the results revealed that Lutjanus fulgens showed an isometric growth pattern (b = 3); Dentex macrophthalmus and Lethrinus atlanticus showed a negative allometric growth pattern (b = 2.9 and b = 2.9). Studies on the condition factor revealed that variations in K values can be attributed to the spawning cycle, the intensity of feeding, and seasonality. The condition factor ranged from 0.013 (Lutjanus fulgens) to 0.015 (Lethrinus atlanticus). This study provides new records of maximum fork length in FishBase for the three species: Dentex macrophthalmus (32 cm), Lutjanus fulgens (39.5 cm) and for Lethrinus atlanticus (37 cm). It is recommended to review the legislation considering the length at first capture (FL₅₀) values of the present study as a measure of protection for this resource in the coastal regions of the South of São Tomé Island.

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